<template>
    <div class="pagination">
        <button :disabled="pageNo==1" @click="$emit('getPageNo', pageNo-1)">上一页</button>
        <button v-if="startNumAndEndNum.start > 1" @click="$emit('getPageNo', 1)" :class="{active:pageNo==1}">1</button>
        <button v-if="startNumAndEndNum.start > 2">···</button>

        <button v-for="(page, index) in startNumAndEndNum.end" :key="index" 
            v-show="page >= startNumAndEndNum.start" 
            @click="$emit('getPageNo', page)"
            :class="{active:pageNo==page}">{{page}}</button>

        <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
        <button v-if="startNumAndEndNum.end < totalPage" @click="$emit('getPageNo', totalPage)" :class="{active:pageNo==totalPage}">{{totalPage}}</button>
        <button :disabled="pageNo==totalPage" @click="$emit('getPageNo', pageNo+1)">下一页</button>

        <button style="margin-left: 30px">共 {{total}} 条</button>
        
    </div>
</template>
  
<script>
export default {
    name: "Pagination",
    props:['pageNo', 'pageSize', 'total', 'continues'],
    computed: {
        //总共多少页
        totalPage(){
            return Math.ceil(this.total / this.pageSize)
        },
        //计算出连续页码的起始数字和结束数字
        startNumAndEndNum(){
            const {pageNo, totalPage, continues} = this
            let start = 0, end = 0
            if(continues > totalPage){
                start = 1
                end = totalPage
            }else{
                start = pageNo - parseInt(continues/2)
                end = pageNo + parseInt(continues/2)
                //纠正不正常现象
                if(start < 1){
                    start = 1
                    end = continues
                }
                if(end > totalPage){
                    start = totalPage - continues + 1
                    end = totalPage

                }
            }
            return {start, end}
        },
    },
}
</script>
  
<style lang="less" scoped>
.pagination {
    text-align: center;
    button {
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 35.5px;
        height: 28px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;

        &[disabled] {
            color: #c0c4cc;
            cursor: not-allowed;
        }

        &.active {
            cursor: not-allowed;
            background-color: #409eff;
            color: #fff;
        }
    }
    .active {
        background: skyblue;
    }
}
</style>